Vehicle-based global-positioning systems (GPS) are capable of providing complete mapping information, including street layout, street names, directions, landmarks, addresses, and the like. However, consumers often have difficulty reading maps, especially when presented on a video screen, and the study of complex information, such as a map while driving, may dangerously distract from the driving task, Vehicle mirror assemblies are desirable locations for an GPS antenna, such as disclosed in commonly assigned U.S. Pat. No. 5,971,552, the entire disclosure of which is hereby incorporated by reference.